Table 1.
UGT1A1 allelic variants and their biologic impact
| Denomination | Variants14 | Allele frequency (ethnicity)15,16 | Expression level | Enzymatic activity | Clinical consequence |
|---|---|---|---|---|---|
| UGT1A1*1 | (TA)6TA | Common allele | 100% | 100% | None |
| TATA box polymorphisms | |||||
| UGT1A1*28 | c.–39_–40 ins TA: (TA)7TA | 29–45% (Caucasians); 42–51% (Africans); 16% (Asians) | Reduced | Reduced | Gilbert’s syndrome, Crigler–Najjar syndrome17 |
| Polymorphisms in the promoter region | |||||
| UGT1A1*60 | c.–3279 T>G | 23–39% (Caucasian); 15% (African Americans); 17% (Asians) | Reduced | Unchanged | Gilbert’s syndrome, Crigler–Najjar syndrome18 |
| Polymorphisms in exon 1 | |||||
| UGT1A1*6 | c.211 G>A p.Gly71Arg | 15–20% (Asians) | Unchanged | Reduced | Gilbert’s syndrome, Crigler–Najjar syndrome19 |
| UGT1A1*27 | c.686 C>A p.Pro229Gln | 5–28% (Asians) | Unchanged | Reduced | Gilbert’s syndrome, Crigler–Najjar syndrome19 |